Tag Archives: Keweenaw stones

Prehnite Adventure

Monday, August 8, 2011

When you’re rock hunting you don’t always know how good the pieces are that you have found. But I spotted a promising prehnite piece today while “driving by”, that I think might be a highlight. Here’s what’s been happening.

The famous (or infamous) lift bridge separating Houghton and Hancock.

We arrived and got settled at the Houghton Campground last Thursday. The campground that the City of Houghton owns has 22 campsites for non-tent camping located right on the channel. This is a very scenic area and it is wonderfully tranquil with the occasional boat or jet ski traveling by. The channel bisects the Keweenaw Peninsula and is a shortcut from the east side of the peninsula to the west side.

Ships can pass thru the channel and when they do the lift bridge is hoisted, causing what the locals refer to as a “traffic jam”. We have been here when the lift bridge got stuck open and it really causes havoc. There is no other way to the north and the hospital is on the Hancock side, so if there is an emergency on the Houghton side (South) there is no way to get across except by boat.

U.P. Thomsonite is really ugly, but surprises await inside the ugly shell.

Today we headed out seeking U.P Thomsonite (which is pink and green Prehnite). This makes wonderful jewelry and often shows chatoyant “eyes“. When you find the stones, they are an ugly brown or bleached white and you cannot know what is inside until you cut the rind off. Picking up the right white/brown stones is the tricky part! Lots of calcite and granite show up as little white stones, but they are not of interest and I had to keep throwing them out of Bonnie’s bucket!

I'm looking for the eroded out Thomsonite.

We were with our friends Chris and Crystal. Prehnite fills voids in basaltic material, that over the years rots away and the Prehnite nodules drop out. You can dig for them in the rotted basalt, or sometimes find an eroded bank where you can simply pick them up. We filled a small bucket in short order from mostly eroded stones. We said goodbye to Chris and Crystal and decided we were done hunting for the day.

But, before we went back to the RV, I decided to explore an old logging road. I poked my head out the window, hoping to see a large agate. Chris got a big one today, and I was hoping to catch up. I saw a large seamed rock in the road and dug it up. A fantastic large seam of eyed Prehnite appeared in the rock. This was the find of the day and I think it will make some great jewelry.

A wonderful Prehnite seam.

While hunting today we found good patches of wild raspberries and Thimbleberries. No bears were about so we ate our fill. YUM!

We have not decided what is on tomorrow’s agenda yet, but we will keep blogging on our adventures here in the Keweenaw. The weather here has been ideal in the mid-70’s, but our best hunting is in the rain, so we are hoping for some soon. It has been very dry here all summer, but there was a nice shower the other night. That’s all for now.

Picture Frame Pendant

I have come to the realization that I have not talked about any of my new designs in quite a while. My latest picture frame pendant has become my recent favorite, and I think these will become a popular items this year.

My interest has not always been in jewelry making and the lapidary arts. I started out in visual arts, especially water color. When you paint a picture, it always looks better in a nicely matching frame, so I thought why not stones? This got me thinking of all my wife’s beads and especially beads made from Michigan rocks and minerals. Between the rocky Great Lakes shorelines, stony gifts from the glaciers, and mineral finds in the Upper Peninsula, Michigan has a real variety of stone to choose from. Many of our Michigan stones are miracles, found here and really nowhere else on earth. What if I could frame these beads in a collage featuring a variety of the most popular of these Michigan stones, making a picture of Michigan Miracles, or Lake Superior Miracles?

I started playing around last year with sizes and designs for my window boxes and this winter decided that the most pleasing shape and size may be a rectangular box of around 20X30mm. Stones can be arranged in pleasing and artistic ways within these confines. Thicknesses of the frames can also be manipulated to protect the beads therein. I have made a couple of much larger frames also that some people enjoy. Larger, or more stones can be used in these larger frames.

The featured stone in a Michigan pendant could be expected to be our Michigan greenstone (chlorastrolite) which is found in small areas of the Keweenaw Peninsula or on Isle Royale. We had some very nice Isle Royale Greenstone beads that were drilled incorrectly. These beads were drilled so when they are strung, you can only see the sides of the beads and not the widest and best part of the greenstone. By using a prong-set on these beads I was able to turn the best faces to the front of the pendants, giving folks a very large size greenstone for a reasonable price. The cost of these gemstones alone is worth our low pendant price. p4080180

I think it is important that the best possible beads be used. If I’m going to make a little piece of art, I want to use the best media (stones), that are available. I am selecting from a nice variety of Michigan miracles: greenstone, Petoskey stone, datolite, jasperlite, thomsonite, firebrick, kona dolomite, epidote, favosite, hematite, prehnite, copper/silver half breeds, and Lake Superior agate.

Wire wrappers should be warned that these pendants take me three times the time that I commonly spend on a pendant! I also think that it helps to have some training in balance, layout, and color and an artistic eye to make these little treasures.

We have posted a couple of these little Miracle treasures on out website, and hope you will experience the same enjoyment wearing and showing these pendants as I do making them.

Prehnite

Sometimes I find wonderful Prehnite on the mine dumps in the Keweenaw Peninsula.

If prehnite forms in veins, as it does in the Keweenaw Peninsula, it generally associates itself with native copper. I love to find these rare pieces that make lovely jewelry, with the apple green of the prehnite surrounding the shiny copper. prehnite-with-copper1

Most of the Prehnite of the Keweenaw is vein Prehnite. In vein Prehnite one cannot notice the chatoyant needle-like crystal structure normally associated with larger non-vein Prehnite pieces such as the gemmy pieces found in Australia and other locals around the world. Feather-like Prehnite crystals are seen in U. P. Thomsonite which is actually variegated and non-variegated Prehnite. Pink, red, and green, and other color combinations can be found, depending on what minerals flowed into the vesicles and veins along with the Prehnite. Locals refer to pastel Prehnite permeated with copper flecks found on the beaches in the Calumet, and also in the Copper Harbor area as “Patricianite”. These Prehnite pebbles can be jewelry grade, and are wonderful to collect as they roll in with the Lake Superior breakers.

Prehnite is very solid, but brittle, so care must be taken when cutting it. Stay away from new grinding wheels and rough grits. Harmonic vibrations can blow apart this material.

High quality Prehnite is available from various locations throughout the world, but when you add the native copper to the Prehnite from the U.P., you can’t beat ours.

Thomsonite and Prehnite

Rockhounding the the Keweenaw Peninsula of Michigan is one of my summer highlights. A distinctive set of stones are found there, many related to the presence of native copper. In this article I would like to talk about thomsonite and prehnite which are different stones, but sometime share the same name.

True Thomsonite may occur in the Keweenaw Peninsula of Michigan, but is generally not associated with copper.

Thomsonite is a zeolite akin to minerals such as tanzanite. Thomsonite is a lovely pink stone sometimes featuring “eyes” and chatoyant sprays. The very best has always been associated with a small area near Grand Marais, Minnesota along the north shore of Lake Superior. The collecting area in that location has been closed to the public for many years, but Thomsonite pebbles still roll up on the beach near Grand Marais. The difficulty lies in most of the beachfront property being private property.

thomsonite

Most of what we use to refer to as Thomsonite from the Upper Peninsula is really copper-bearing Prehnite, or what is sometimes referred to as Patricianite. If you find what you believe to be Thomsonite and it contains specks of copper, it probably is Prehnite. The inclusions in the Prehnite are endless and create lovely pastel colors. Often “eyes” are present as are variegated type feathery patterns. We refer to these gemstones on our website as U.P. Thomsonite (this is what the locals call them also).

U.P. Thomsonite, in my opinion, is the most remarkable gemstone found in the Keweenaw. The striking chatoyancy and pastel colorations of this stone are something to behold. It is impossible to photograph the chatoyancy of true Thomsonite and U.P. Thomsonite as you really need to move the stones back and forth to see this effect. Thomsonite is much more expensive and scarce than Prehnite, but many people find the U.P. Thomsonite more attractive.

Good, jewelry-grade Patricianite is still hard to come by. It took me ten years to locate a spot to dig this wonderful stone. The locals will not easily give up their best rock hunting locations, so you may be on your own when it comes to finding U.P. Thomsonite.

Our website features some of the finest Thomsonite and U.P. Thomsonite available.

Native Copper

The largest and greatest deposits of native copper ever discovered occur in Michigan’s Keweenaw Peninsula. These copper deposits have been exploited since prehistoric Native Americans used hand tools made of rocks to chisel out the almost pure copper from exposed surface areas.

Native copper is very rare throughout the world. Copper deposits are not ordinarily comprised of large masses of almost pure copper. The copper from the Keweenaw is most often “polluted” with silver, making it even more conducive to electrical uses. copper

The habits of copper growth are too numerous to list, but one of the most coveted by Keweenaw-area collectors are silver and copper combinations known as “half-breeds”. Beautiful crystal copper formations are also sought, as are copper-included minerals such as Datolite, Prehnite, and Greenstone.

The history of the Copper Country is interesting to study and many wonderful books have been written on the subject.

We sell native copper, both cleaned and raw, as well as special pieces like the aforementioned half-breeds. We also have raw chunks of copper that have been through the hammer mills and most likely carried off by miners in their lunch pails. Another interesting throwback to the copper days is Firebrick, almost impossible to find now. Bricks lined the smelter walls and over time became permeated with molten copper. After the mines closed, some of this material was rescued when the smelters were closed, back in the 1960’s.

Currently no producing mines are left open in the Keweenaw, the tunnels are flooded, and the discard piles are gradually being crushed for road gravel. I have seen collecting opportunities in the Keweenaw declining rapidly over the past 20 years as old mine discard piles disappear, and collecting areas revert to private property. Much of the gemstone material I used to collect is now impossible to obtain in the field. Now is the best time to invest in jewelry and specimens from the Copper Country while the prices are still affordable.

A few mines are still open for tours: the Delaware Mine between Calumet and Copper Harbor, the Adventure Mine near Ontonagon, and the Caledonia Mine, also near Ontonagon. The Caledonia Mine offers collecting opportunities both underground and on the surface by appointment. Specimen collecting is still underway by the owner of the Caledonia, Rich Whiteman and his crew.

We offer the very best jewelry manufactured from rare copper country gemstones. Many of the materials we use are purchased from collectors in the area or found by us in our rockhounding forays to the area each year. Our beaded bracelets combine many U.P. stones including agates, epidote, and kona dolomite as well as the copper-related stones. Our Datolites sometimes have great bits of copper in them–Copper Datolite with Epidote, and Datolite, Copper Lightning. We use only the finest quality rough materials to create our finished products, and truly believe our U.P. jewelry line is the finest anywhere.

Datolite Jewelry

Datolite is a mineral closely associated with the copper mines in Michigan’s Keweenaw Peninsula. The natural coloration of Datolite is white, but I have seen or collected Datolite in gray, green, pink hues, mauve, brown, red, orange, black, and the most rare, yellow. Any combination of these colors is possible. Small specks of copper and other inclusions may be present.

Datolite nodules, rough and cut

One of the things that make Keweenaw Datolite unique is its nodular form. Nodules are difficult to locate on a rock pile, because they blend into the background rock. A small glint of color or a rounded cauliflower shape might be the only clue that this valuable gemstone is hiding right in front of your eyes. Crystals of Datolite also occur, but to a lesser extent than the nodules. Datolite also can form in seams.

Datolite makes wonderful and colorful jewelry, and our Datolites represent many mines in the Keweenaw. I hunt Datolite as well as purchase specimens found by others to produce my jewelry. Datolite from the Keweenaw, as well as other minerals, is becoming scarce due to several factors including the mine dumps being on private property, or being ground up and hauled away for road fill. I have seen a steady price increase in Datolite in the past few years as the sources vanish. Now would be a good time to invest in these beautiful and rare gems!

Greenstone and Datolite have been designated as Michigan’s only true precious gemstones. Quality wire-wrapped Datolite jewelry is my specialty. If you have a special request for Datolite contact me.

For even more on the colors of Datolite found in each mine, click on this link to Jeff Anderson’s web site Dwarves’ Earth Treasures.